1. Field of the Invention
This invention relates to a prober for directly measuring the electrical characteristics of electronic devices and the method of measuring same, and relates particularly to a prober suited to the measurement of the electrical characteristics of semiconductor devices with a fine structure.
2. Description of the Prior Art
Determining the internal state of operation of a semiconductor device is essential to semiconductor device research and development. The apparatus conventionally used for this kind of determination is a prober for the electrical measurement of semiconductor devices. Such a prober is first positioned and then a certain amount of force is applied with the tips of its probes to make electrical contact between contacts on the semiconductor device and the probes, and thereby the electrical characteristics (current, voltage, etc.) at various locations on the device are measured using two or three probes, or it may be used together with a stage that varies the temperature of the semiconductor device to measure the electron mobility or the like, and thereby determine spatial electrical characteristic information about the interior of the semiconductor device.
Since the aforementioned conventional probers for the electrical measurement of semiconductor devices have probe tips of a size on the xcexcm order or greater, the contacts at various locations on a semiconductor device with a fine structure are smaller than the size of the probe tips, so it is not possible to measure the electrical characteristics directly. In addition, even with semiconductor devices having design rules of a size of xcexcm or greater, the probers for electrical measurement do not have drive means for driving the prober in sub-xcexcm order units, so they are inappropriate as a means of directly measuring the potential distribution within a semiconductor device. Moreover they have a problem in that the contact pressure of the probe tip destroys the contact of the semiconductor device.
For this reason, the electrical measurement of semiconductor devices was performed instead by packaging the semiconductor device for radio-frequency measurement and then the probes were put into contact with electrode contacts that extended out from the semiconductor device. However, as semiconductor devices reach finer geometries, probers for measuring electrical characteristics that directly measure various locations of the semiconductor device have become necessary.
In addition, the effects of the surfaces and interfaces on the internal structure within the semiconductor device are not negligible at the time of measuring the electrical characteristics, but rather the appearance of quantum effects arising from the miniaturization of the semiconductor devices have made the interior electronic structure of the semiconductor devices even more complex. For this reason, parameters such as the potential distribution and the like which are necessary for the design simulation of semiconductor devices cannot be measured with conventional probers, so research and development of fine-geometry semiconductor device technology is in a difficult predicament.
In the design of future fine-geometry semiconductor devices, the direct measurement of electrical characteristics at various locations of a semiconductor device with a probe will be essential to find the size of electrodes or other fabrication errors, and the potential distribution or other parameters necessary for simulation, so that by performing comparative studies of these parameters against the simulation, it is possible to increase the operating speed of semiconductor devices, raise their switching ratios, reduce their power consumption and perform various other kinds of optimization.
For this reason, there is a need for the development of technology that can directly measure the internal potential distribution within fine-geometry semiconductor devices and semiconductor devices, along with the size of electrodes or other fabrication errors and the like.
The present invention came about in consideration of the aforementioned situation and its object is to provide a prober for electrical measurement that is capable of direct measurement of electrical characteristics required for fabrication technologies for fine-geometry semiconductor devices, and also provide a measurement method using said prober.
In order to achieve the aforementioned objects, the prober for electrical measurement of the present invention comprises: a probe with a sharp tip, drive means for driving said probe in the direction of the x-, y- and z-axes on the nm order, an x- and y-axis drive circuit that supplies drive current to said drive means for driving in the direction of the x- and y-axes, a first electrical circuit for detecting the tunnel current between said probe and the semiconductor device to be measured, a z-axis drive control circuit that supplies drive current to said drive means for driving said probe in the z-axis direction by using the output from said first electrical circuit as feedback input, a second electrical circuit that applies a variable DC bias voltage between said probe and semiconductor device and detects the current and voltage between said probe and semiconductor device, a circuit for providing output to the z-axis drive control circuit of a signal that halts the driving of said probe in the z-axis direction upon the detection of an abnormal increase in the current flowing in said second electrical circuit, a switch that connects said probe to either said first electrical circuit or said second electrical circuit, a controller that supplies signals for driving said probe in the x-, y- and z-axis directions, setting tunneling current signals for the z-axis drive control circuit and setting voltage signals for the variable DC bias voltage of the second electrical circuit, and acquires x, y and z positional information for said probe along with the voltage, current and potential information from the second electrical circuit, and stores and performs image processing on said information, and a display device that displays said information and image information.
As the means of driving the aforementioned probe on the nm order, a piezoelectric element actuator or inchworm drive may be used.
The probe can also be driven to the desired position while using interatomic forces, temperature or light instead of the aforementioned tunnel current to detect the state of contact between the probe and the surface of the semiconductor device.
In addition, the method of measuring electrical characteristics using the aforementioned prober according to the present invention comprises the steps of: causing a sharp probe to scan over the surface of a semiconductor at a distance at which the tunnel current phenomenon occurs and based on the semiconductor surface approach position data thus obtained, accurately positioning said probe at a semiconductor surface approach position corresponding to the desired position on the semiconductor surface, driving said probe lower in the z-axis direction toward the semiconductor surface until an abnormal increase in current flows through said probe, applying a voltage to said probe, and directly measuring the current and voltage at the desired position on the semiconductor device.
The probe can also be driven to the desired position while using interatomic forces, temperature or light instead of the aforementioned tunnel current to detect the state of contact between the probe and the surface of the semiconductor device.
As described above, the present invention uses a conductive probe with a tip radius of not more than 0.02 xcexcm or less as the probe, and by using a drive mechanism that drives the sharp probe to approach a position near the semiconductor device with nm order accuracy until an abnormal increase in the current flowing in the sharp probe is detected, thereby detecting the electrical contact between the sharp probe and the semiconductor surface, it is possible to put a sharp probe into electrical contact with the semiconductor surface without destroying the semiconductor device, thereby directly measuring the electrical characteristic of a specific location on a semiconductor device with a sharp probe and an electrical characteristic measurement circuit.
The other objects and other characteristics of this invention will be further clarified in the following detailed description based on the appended drawings.